Electrostatic paint spraying system



April 18, 1961 .1. KOZINSKI ELECTROSTATIC PAINT SPRAYING SYSTEM 2 Sheets-Sheet 1 Filed March 4, 1954 i I L OBJECT T0 BE PAINTED ATTORNEY United States Patent 0:

Joseph Kozinski, Chicago, Ill., assignor to H. G. Fischer & Co., Franklin Park, 111., a corporation of Illinois Filed Mar. 4, 1 954, Ser. No. 414,009 1 Claim. (Cl. 239-15) This invention relates toa paint spraying system, .and particularly of the type involving the use of high potential electrostatic fields for directing particles of paint toward the object to be painted. Electrostatic field paint spraying systems depend upon the fact that paint to be applied to an object is finely divided and then disposed in an electrostatic field. The electrostatic field either terminates at or passes through the article to be painted. The paint particles as electrified fine particles move along lines of potential gradients.

The efficiency of an electrostatic paint system depends, among other things, on the fineness of the paint particles and the velocity attained by the paint particles just prior to their impact upon the article to be painted.

While a variety of means for obtaining paint in finely divided form and disposing the same in an electrostatic field are known, such means are relatively complicated or inefficient. The quick-drying characteristics of paint or lacquer or whatever material is used, together with the high potential insulation requirements, render this problem diflicult of solution. Furthermore, the requirement that a paint spraying system be simple, safe and foolproof and also be free from service trouble, imposes additional requirements.

In accordance with this invention, a simple system is provided whereby the material to be applied, such as paint, lacquer, varnish or the like, is first atomized in asimple'and effective manner and is disposed in an electric field so that the finely atomized particles may move in the proper direction toward the article to be covered.

In order that the invention may be understood, exemplary embodiments will now be disclosed in connection with the drawings with the understanding, however, that modifications and variations are possible, all within the scope of the invention as defined by the appended claim.

Referring to the drawings:

Figure 1 is a partly diagrammatic view of a paint spraying system embodying the present invention.

Figure 2 is an elevation of the atomizing means.

Figure 3 is a sectional detail on line 3-3 of Figure 2.

Figure 4 is a view similar to Figure l but showing a modification.

Referring to Figures 1 to 3 inclusive, the paint or lacquer or whatever material is being applied may be stored in paint tank of any desired construction. Tank 10 may be as large as necessary and may be of metal or an insulating material and may have a cover or not, as desired. Tank 10 has outlet 11 from the bottom thereof to which is attached pipe 12. Pipe 12 is preferably of insulating material and may be of flexible hose of rubber or of plastic material having the desired chemical characteristics and having good electrical insulating qualities. A valve is provided for controlling the flow of liquid from tank 10 into pipe 12.

Pipe 12 has end 13 which is provided with a suitable slip joint engaging hollow shaft 14 of motor 15. Motor 15 may be of any desired construction and because of the possibility of explosion, may be of the enclosed type.

2,980,338 I Patented Apr. 18, 1961 ii. E

Motor 15 is different from a conventional motor only in having a hollow shaft 14 rather than a conventional solid shaft. Motor 15 may be supported in any suitable manner provided, however, that the entire motor is in- 6 sulated from ground for the full potential used in the electrostatic system.

Motor-15 supports concave electrode 17, the electrode being stationary and being rigidly supported from the motor casing an any suitable fashion. Electrode 17 may 10 have any desired shape and as illustrated here, has the general shape of a hollow bowl. The electrode may consist either of metal, such as copper, aluminumor iron, or may consist of any insulating material having a metal film of copper, aluminum, iron or any other material de- 15 sired. Electrode 17 has centrally disposed aperture 18 (Figure 3) through which hollow motor shaft 14 passes. The end of motor shaft 14 has rigidly attached thereto spinner 20 for atomizing liquid.

Spinner 20 has tubular attaching portion 21 for en- 20 gaging motor shaft 14. Attaching portion 21 forms part of spider 22 extending outwardly of the spinner and terminating in annular flat ring 24. Ring 24 has a number of radially disposed blades or vanes 25. Spider 22 also carries fixture 27 defining chamber 28 for capping the open end of motor shaft pipe 14. Fixture 27 may as? sume a variety of forms and, as shown here, consists of circular disc 29 and fiat annulus 30 joined together by rim 31. Rim 31 has a number of apertures therethrough for connecting chamber 28 within the fixture to the ex- 30 terior of the fixture. At'these apertures are stub tubes 33 rigidly attached to rim 31 so that in effect the fixture has a number of radially directed tubes. Preferably, these tubes are so arranged as illustrated in Figure 2 that the tubes are along radii which extend between ad- 35 jacent vanes, the tubes themselves terminating short of the inside edges of the'vanes. The fixture and tubes are disposed so as to lie within the spread of the vanes as illustrated in Figures 1 and 3. Y

The spinner will be rotated at high speed by motor 15, paint being supplied to chamber 28 through the hollow shaft of the motor. Motor 15 is energized by secondary 36 of transformer 37. Transformer 37 has primary 38 for connection to a conventional power circuit such as, for example, a 110 volt cycle line. Transformer 37 has secondary 36 insulated for high potential from primary 38 and from the iron core. Secondary 36 is connected by suitable leads 40 to the winding of motor 15.

As will be readily understood, electrode 17 must be at a high direct potential with reference to ground for proper operation of the paint spraying system. In accordance with this invention, electrode 17, motor 15 and secondary 36 of the transformer will all'be at high potential and will be adequately insulated from ground and also will be so designed or protected as to prevent an operator from contacting the same while the potential is being applied.

The dotted lines indicate the parts of the system at high potential. Inasmuch as paint supply tube 12, or at least part of it, will be of insulating material, hollow 60 shaft 14 of the motor will be electrically insulated from the parts of the paint supply which might normally have to be handled, and no special means for insulating the paint tank and at least part of the piping will be required.

The object to be painted, generally indicated by 40,

may be any desired article. As a rule, the article to be I painted may be of metal or have a metal film thereon so that it functions as an electrode and may be at a suitable potential with respect to electrode 17. However, in certain instances, electrode 40 cooperating with electrode 17 may be disposed in back, that is, to the left of the article to be painted, so that the article is in the 7 preferably of metal.

direct line of travel between electrode 17 and the cooperating electrode. In other instances, electrode 40 may I be a metal'screenor grille 'in front of the work so that the paint particles pass through electrode 40..

"The polarity of electrode 40 and electrode '17,,wil1gvary depending upon. the type' of systemandfthe material used 1 forpiainting or-covering'. Thus in certainj,cases electrode 17 mayi haveftob e negative to electrode 40 and in' other gametes instances, the polarity must be reversedflThis is aQsimp le matter,and, as..a rule, consistsin merelyljrever'sinigf'ertaiu'high tension leads orma'nipulatingla switch in a p w upply.

The ,power supply for obtaining"aidesired :higli'poten tialis notishown, such supplies being wellrknown and available inptheindustry. Asa rule, aipower supply for -a' sy stemjof thischaracter must generate or provide .p'o- I tentialsjoflthe order of 100,000yoltsor more, the current drain' as a'ruleb'eing'small and in the order of milliamps. 7

Suitable safety'interlocks maybe provided "to prevent an operator from touching orfhandlingithe motor or electrode 17. As a rule,the objectto be painted, ifof metal, or electrode 40 cooperating therewith, will be at ground potential while electrode 1 7 will be either at ahighpositive or negativepotential with respect to' ground: v The revolution of the spinner willp'r'ovide a pumping action independently of the tendency of paint to .flow from the tank to the spinner. Infact, the tank for'paint need not necessarily be located above the spinner, and in many instances, the tank may be'locat'ed belowthelevel of the spinner with the supply pipe 12 extending down- .wardly into the tank firom the bottom thereof. The high speed of the pinner'will-serve to' throw out the liquid paint or varnish or whatever is'being used, the blades striking the liquidand Vato'mizing the same to fine particles. The atomized particles have already acquired electric charges. due to the high potential of motor shaft 14, which will be of steel, and the various spinner parts,

cipally to shape lines of electrical force going to electrode 40. Thus electrode 17 need be shaped only to have a desired efiEect on the shape of'theelectric field. The atomizing motor maybe conventional even though at high potential. Instead of the atomizing means illustrated other atomizing means may be used'in connection with the motor. Referring to Figure 4, a modification is'illustrated; In-

L'paint supply pipe and atomizer. I

stead of an electric motor, an air motor or turbine 15' is provided. The" air turbine has 'a "hollow shaft resembling the motor shaft. fifl'he air turbine is supplied by hose 45 of insulating material connected to a compressed air source 46. A valve for controlling the air supply ,to turbine 15 is provided. The part of the system to be insulated is shown generally by the dotted rectang'le. The right potential connections go to 'the object to be p ainted'and airturbineio'r'other metal part contacting the 'lnstefad' ofairflikjuid may 'be used. In such case, a I

supply and return pipe would be necessary.

What isclaimedis; v p i For use in an electrostatic-type paint spray system, the combination of an air-turbine having a stator and rotor including a hollow metal shaft, a hollow rotary coupling and stationary pipe providing 'a connecting means between one end of said hollow shaft and a stationary coating materialta'nk; said connecting means including high potential insulation along the line -of coating material travel 'between'said shaft: and{ said tank, a source of power, a stationary metal bo'wl rigidly supported onsaid stator, said bowl being disposed adjacent the other end of said rotor shaft,-atomizin g means*supported on said shaft at-the other end thereof and rotatable therewith, said atomizingmeans operating within the region enclosed by said bowl-to atomize the coating material, means for connecting said turbinewith said source of power; saidlast mentioned means-including high potential insulation in said connecting path, means for electrically insulating said turbine from ground for the full potential of said electrostatic" system, and means tor-maintaining said entire turbine and atomizing mean's'at high potential Electrode 17 is providedprinand said'tankand said source of power at ground. 

